where \(C_{\rm d}\)  and \(C_{\rm r}\)  are the channel fading variables related to the wavelength, channel status, and angle of departure (AOD), and \(C_{\rm r}\)  is also related to the angle of arrival (AOA), the material and size of ris element [1]}; \(G_{\rm B}\)  and \(G_{\rm u}\)  denote the antenna gain of the bss and users, respectively, and here we assume \({C_{\rm d}}{G _{\rm B}}{G _{\rm u}}=-30\)  dB and \(C_{\rm r}{G _{\rm B}}{G _{\rm u}}=-40\)  dB [2]}; \(\kappa \)  denotes the path loss exponent, and the path loss exponents of the BS-RIS link, RIS-user link, and BS-user link are set as \({\kappa _{\rm BR}}=2\) , \({\kappa _{\rm Ru}}=2\) , and \({\kappa _{\rm Bu}}=3\)  [1]}, respectively.
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